So it’s rather weird that “psychologists base most of their generalizations about human nature on studies of our own narrow and atypical slice of human diversity. Among the human subjects studied in a sample of papers from the top psychology journals surveyed in the year 2008, 96% were from Westernized industrial countries . . . , 68% were from the U.S. in particular, and up to 80% were college undergraduates enrolled in psychology courses, i.e., not even typical of their own national societies” (8).

Some social scientists have given this phenomenon the acronym WEIRD: “Western, educated, industrialized, rich, and democratic.” And Diamond says they are “literally weird by the standards of world cultural variation” in areas like “visual perception, fairness, cooperation, punishment, biological reasoning, motivation to conform, making choices, and concept of self.”

Diamond modestly suggests that psychologists could generalize more accurately if they broadened their samples.